Corrected optical objective comprising six simple components axially aligned and air spaced apart



June 24, 1952 COOK 2,601,592

CORRECTED OPTICAL OBJECTIVE COMPRISING SIX SIMPLE COMPONENTS AXIALLY ALIGNED AND AIR SPACED APART Filed March 5, 1951 P R R +-/702 R5 +6025 R7 --4 R9 +5000 +2967 -9009 /970 Inventor Q OPDON H C OOK B7 Attorneys Patented June 24, 1952 GDBREGIE Y HJCAL QB EC'IIVE {30M- :-rmsnvo s x. oomommrs ma n spinner) "am .smcen Geek; Leicester, England, astn 'iml 'rwilayl r 1&"H9b591 Limit d,

Lei es.

llfiglm lvqa Briti h manna when Mai-t1: 5.51951, sea: N 213,833 InGreatDritain February '15, 1951 1 I invention rel-ates to an optical obieetive, more ':especiafiy tor photographic "purposes, oerrested rio'r spherical and chmn'iatio aberrations, coma, astigmatism, neldeurvatume vand distortion,

and-comprising sixsimple components,- three on iii-exams. (oi. 58 51) either side of a diaphragm, the inner and outer components being convergent "whilst the. middle component in each half-is slivepgent, the 1 surfaces of the {our oonvergent'nomponents omit the surioxzes or the nivergent components and of the convergent inner components ail-being i eonoavle.=to-the.diaphragm..

- {Else inventionhasior its object to provide 'a' welheozwected objective at this type having amen rehtiveapertureand wide eoverin'g pewer smialsohawing improved-correction for some: spherical aberration "and oblique spherical aberration;

The invention has the further advantage that-it makesit possible to have" diameters larger than are needed for-the axial. beam alone in outer-t0 avoia the vienetting: which would otherwise: be objectionable with the wide angular fieki coverallin the obgective -according-to thepn'asentinven i2 tune of such surfaces respectively iving between F/3 and 515 in the front half and between F/Z-and e inxthemearhaifoi'the obiecthre. v

ltyshonm'bemade clear that the terms 'fiiront" and rear are used herein in accordance 'Mth the usual convention to indicate the sides of the objective respectively nearer to and further 20m the-longer conjugate.

the objective be corrected to cover a semi-angular fleid' greater than '30 degrees, the mean eefraotive indiees N3 N1: N6 of the mate: rialsoi tne foul-convergent components preterablvbear such relationship to --:the mean refine tive indi'ces' N2 N: :of the -materials' ot the twodiszesgent-eommnents-that (Niel-N5) [12 .06,

IEhe accompanying drawing illustrates a preferred praeticai example cat-objective according to the-invention -.and=n-umerica1i data 110!- this iextion, the sum of the equivalent focal lengths of? the two convergent inner oomponents lies'between 1 .8F-and -2-6Fi-where 1 is the equivalent i'ocai length of. the whole objective, and the arithmetie mean between the positive values of the radii-of curvature .of' the outer surfaces of suehinner components iiesflkFandAtI-E- f.

The arithmetiemean of theex ial distances ibetween the outer surfaces of the convergent iouter components and the inner surfaees of the edit;- centdivrgent components preferebiyflies between sew-end .171 'l-ne-arithxnetiemean of the axis-1 air. separationsbetween the divergent components and the ponverg'ent inner components end the arithmetic meanof the axial air -sepa-'-- rations between the divergent components and the-convergent outer components preferably each liebetween-miF-and f P'rne arithmetic mean of the positive valuesof the radii ofcurvature of the inner aux-{was of the divergent components preferably lies between .HF and 35F. The outer susiaces'of -the divergentcomponents are also preferably concave towards the diaphragm; the radii of curvature- 0f such surfaces respectively lying between F753 and -5F in the. Irontimif ambetsveen. B34 2 and in the rear-half OIjtheODiQGtiVm v a erithmetic. meaniof. the positive. values of he man 93 u ste eos the es er nr cesm the oonver gent' utex-:,commn nts etween--18Eand-3. in ensq ieees o such outer components are also preferably a e towa ds the. s iaphnssm the win a nurseample are given inthe *foilowing'table, in which R173 2 representithe'radii of curvature of the iDdi fYiGUSlI- SHFIQCGSOI the objective, the indicating that thesurface is veonvex'to the tront and :thenegative sign'that it is coneave thereto; 131F132 represent the axial thick messes-or the various elements and Si 5.:

represent: the air separations-"between the components; The'tabie also gives meanness renumbersoi the nisteriais oi tne' various-elements;

'T-hicknessor new ninseperav Mum-z tion I pgi gamma Inflexmr;

I I. i

In this example, which is corrected to cover a wide angular field of semi-angle 35 degrees, the diaphragm is located approximately midway between the surfaces R6 and R7. All six components are of meniscus form with their surfaces concave to the diaphragm.

The equivalent focal length of the convergent tances between the outer surfaces of the convergent outer components and the inner surfront inner component is 1.1191 and that of the rear inner component is 1.160F,so that the sum of these focal lengths is 2.2791 The arithmetic mean of the positive values of the radii R and RslS.3483F. I

The axial distances between the surfaces R1 and R4 and between the surfaces R9 and R12 are respectively .125F and .110F, so that their arithmetic mean is .11'7F. The arithmetic mean of the,

two outer air spaces S1 and S5 is .032F' and that of the air spaces S2 and S4 is .025F.

The arithmetic mean of the positive values of the radii R4 and R9 is .1836F. and that of the radii R1 and R12 is .24201.

The arithmetic mean of the mean refractive indices of the materials of the four convergent components is 1.6343 and exceedsthatfor the two divergent components, namely 1.6195, by

The invention makes it possible to have diameters for the various components larger than is requiredforthe axial beam alone,- and such larger diameters are very valuable in facilitating cor-r rection for oblique aberrations and contribute towards the wide angular field which canbe covered byobjectives according to the invention. Thus, in the example given above, the effective diameters of the individual surfaces may conveniently be .363 for R1 and R2, .3F for R3, .2F' for the chamfer of R4, 24$ for R5, .19F for the chamfers of R5 and R1, .24F' for Rs, .181 for the chamfer of Re, .29F for R10, and .331" for R11 and R12. Theinsertion of equals signs in the radius columnof the table, in company with plus and minus signs which indicate whether the surface is convex orconcave to the front, is for conformitywith the patent ofiice custom, and it is -to be understood that these signs are not to be interpreted wholly in their mathematical significance. This sign, convention agrees with the mathematical sign convention required, for the computation of some of the aberrations ,including the primary aberrations, but different mathematical sign conventions are required for other purposes including computation of some of the secondary aberrations, so that a radius indicated for example as positive in the tables may have to be treated as negative for some calculations as is well understood in the art.

What I claim as my invention and desire to secure by Letters Patent is:

1. An optical objective corrected for spherical and chromatic aberrations, coma, astigmatism, field curvature and distortion, and comprising six simple components axially alined and-air spaced apart, a diaphragm approximately in the middle of the objective having three of such components on either side thereof, the two outermost and the two innermost of such components being convergent whilst the other two are divergent, the outer surfaces of the outer components and the inner surfaces of the divergent components and the surfaces of the inner components all being concave towards the diaphragm, the sum of the equivalent focal lengths of the two convergent inner components lying between 1.8F and 2.6F where F is the equivalent focal length of the whole objective, the arithmetic mean between the faces 'of the adjacent divergent components lies between .OSFI' and..17F.

3. An optical objective as claimed in claim 2, in which the arithmetic mean of the axial air separations between the divergent components and the convergent inner components and the arithmetic meanof the axial air separations between .the divergent components and the convergent outercomponents each lie between .01F

and .1F.'

4.- An' optical objective as claimed in claim 1,

in which the arithmetic mean of the axial air between F/2 and w in the rear half of the objec separations between the divergent components and the, convergent inner components and the arithmetic mean of the axial airseparations between the divergent components and the convergent outer components each lie between .OlF' and.1F.'

5.- An optical objective as claimed in claim 1,

in which the arithmetic :mean of the positive values of the radii of curvature of the inner surfaces of the divergent componentsliesbetween .l-lF-and .25F; V 6. An optical objective as claimedin'claim 1, in which the outer-surfaces of the divergent componentsare concave towards the diaphragm,the radii'of curvature of such surfaces respectively lying between-1V3 and SF in the front half and between F/z and w in the rearhalf of theobjective. a I

7. :An optical objective as claimed in claim 1, in which the outer surfaces ofthe divergent components are concave towards the diaphragm, the radii of curvature of such surfaces-respectively lying between F/3 and 5F in the front half and tive, the arithmetic mean of the positive :values of the radii of curvature of the inner surfacesof the divergent components lying between .llF-and 8. An optical objective as claimed in claim 1,. in which the arithmetic mean of the positive values of the radii of curvatureof the two outermost surfaces of the objective lies betweenllsF 9. An optical objective as claimed in claim l,v

-, in-which the inner surfacesof the outer components are concave towards the diaphragm and their'radiipfcurvature lie respectively between.

F/3 and 5F in the front half and between F/2 and in the rear half. Y

10. An optical objective as claimedin claim-1,

" in which the inner surfaces of theouter. components are concave towards the diaphragm and their radii of curvature lie respectively between F/3 and 5F in the front half and between F/2- and w in the-rear half, the arithmetic mean of the positive values of the radii of curvature of the two'outermost surfaces of the objective .lying' between .18F'and .31

11. An optical objective as claimed inclaim '1,

in which the arithmetic mean of the positive values of the radii of curvature of the'inner'surfa'ces'of the divergent components lies between in which the outer surfaces of the divergent components and the inner surfaces of the convergent outer components are concave towards the diaphragm, the radii of curvature of such surfaces lying between F/3 andfiF in the front half and between F/ 2 and w in the rear half of the objective.

13. An optical objective, corrected for spherical and chromatic aberrations, coma, astigmatism, field curvature and distortion, to cover a semi-angular field greater than 30 degrees, and comprising six simple components axially alined and air spaced apart, a diaphragm approximately in the middle of the objective having three of such components on either side thereof, the two outermost and the two innermost of such components being convergent whilst the other two are divergent, the outer surfaces of the outer components and the inner surfaces of the divergent components and the surfaces of the inner components all being concave towards the diaphragm, the sum of the equivalent focal lengths of the two convergent inner components lying between 1.81 and 26F where F is the equivalent focal length of the whole objective, the arithmetic mean between the positive values of the radii of curvature of the outer surfaces of such inner components lying between .22F and .44F, the materials of the components of the objective being such that where N1 N3 N4 N6 are the mean refractive indices of the materials of the convergent components and N2 N5 are those of the divergent components.

14. An optical objective as claimed in claim 13, in which the arithmetic mean of theaxial distances between the outer surfaces of the convergent outer components and the inner surfaces of the adjacent divergent components lies between 0.8F and .17F'.

15. An optical objective as claimed in claim 13, in which the arithmetic mean of the axial air separations between the divergent components and the convergent inner components and the arithmetic mean of the axial air separations between the divergent components and the convergent outer components each lie between .01F and .1F.

16. An optical objective as claimed in claim 13, in which the outer surfaces of the divergent components are concave towards the diaphragm, the

radii of curvature of such surfaces respectively.

lying between F/ 3 and 5F in the front half and between F/ 2 and w in the rear half of the obj ective, the arithmetic mean of the positive values of the radii of curvature of the inner surfaces of the divergent components lying between .llF and 251?.

17. An optical objective as claimed in claim 13, in which the inner surfaces of the outer components are concave towards the diaphragm and their radii of curvature lie respectively between F/3 and 5F in the front half and between F/2 and w in the rear half, the arithmetic mean of the positive values of the radii of curvature of the two outermost surfaces of the objective lying between .18F and .3F.

18. An optical objective as claimed in claim 13, in which the arithmetic mean of the positive values of the radii of curvature of the inner surfaces of the divergent components lies between .11F' and 25F, and that of the outer surfaces of the convergent outer components lies between .18F and .3F.

19. An optical objective as claimed in claim 13, in which the outer surfaces of the divergent components and the inner surfaces of the convergent outer components are concave towards the diaphragm, the radii of curvature of such surfaces lying between F/3 and EB in the front half and between F/2 and w in the rear half of the objective.

GORDON HENRY COOK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,031,792 Richter Feb. 25, 1936 2,116,264 Hasselkus et a1 May 3, 1938 2,325,275 Rayton July 27, 1943 FOREIGN PATENTS Number Country Date 3,398 Great Britain of 1905 168,923 Great Britain Sept. 12, 1921 487,453 Great Britain June 21, 1938 

